The Emdrive won't work, in my opinion.

What's the Emdrive?

You should read about the Emdrive elsewhere, then come back here. Most people say that it works. I think they're all wrong.

Why should we listen to you? Who are you?

It doesn't matter who I am. I will spell out the facts very clearly on this page. Make up your own mind.

How can all those other people be wrong?

I don't care. That's their problem.

I read about the Emdrive, and it seems very complex.

No, it's very simple. It's a container, shaped like this;

Fill it with microwaves, and it's supposed to fly upwards.

Are you kidding? Isn't there more to it?

There's a lot of difficult math, to figure the performance of the Emdrive. We can skip the math; let's just say the performance is supposed to be amazing if the thing is correctly tuned.

There's just one more detail you need to know; the microwaves bounce up and down, top to bottom.

OK, but why would that make it fly?

The microwaves press against the container. They press harder against the top than the bottom. For that reason, it's supposed to float upwards.

Oh, I think I get it. The top is wider.

Yes! The top gets a bigger push than the bottom. The inventor used math to prove this.

Hang on! You ignored the SIDES.

I was hoping you'd notice that. The sides can ALSO get pushed. And that is a DOWNWARD push.

Why are you so happy that I noticed the sides?

Because the inventor of the Emdrive ignores them!

He published a technical paper, full of calculations about the Emdrive. It's impressive, but he IGNORES THE SIDE WALLS.

Then he could get the wrong answer!

I think he DOES get the wrong answer. He says the Emdrive will float up into space; I think it won't. The sides, as well as the bottom, will push it down, and cancel the upward push.

That's a huge omission! Did nobody notice it?

Plenty of people noticed this problem, years ago, and they asked about it. He said the sidewall force was "minimised" and "nonlinear" but he didn't publish the calculations, as far as I know.

I think that nobody should take the man seriously at all, until he provides the missing calculations.

But the inventor of the Emdrive seems pretty clever! He uses the Einstein theory!

I don't think that he understands the Einstein theory. But let's look at something much more basic.

Take a look at page 4 of his technical paper. He imagines the Emdrive filled with a fluid instead of microwaves. As a result, there is a net force. And he says;

"the resultant force would merely introduce a mechanical strain in the waveguide walls"

A high school student should know that this is wrong! An object will accelerate if there is a net force on it.
How did he make this mistake? It's the same mistake he already made before. He IGNORED THE SIDES.

But, didn't NASA just test an Emdrive successfully?

That depends on what you call "success". NASA measured a tiny force during a test of an Emdrive. It is not clear whether this was a genuine effect, or a just problem with the experimental setup.

NASA also tested a "Cannae drive". This is similar to the Emdrive, but more advanced.

Cannae Drive? What's the difference?

With the Emdrive, a high school physics student can read Roger Shawyer's theory and see that something is wrong. The Cannae Drive has a much more complex shape, and it requires a university-level student to understand that it won't work. That's the advance; from high school to university.

Are you saying that NASA would not notice a problem in the Emdrive theory?

I can't speculate about their competence or their motives. All I can say is, there it stands, and it's invalid.